An O-acetylated glucomannan from Bletilla striata: Structural characterization and ADP-dependent platelet-activating...

Previous work demonstrated that crude Bletilla striata polysaccharides exhibited hemostatic effects against gastric bleeding through the activation of ADP pathway, whereas their key homogeneous active constituent remains structurally undefined. Herein, bioactivity-guided fractionation afforded a novel homogeneous polysaccharide BSP-60 (6271 Da), identified as the core hemostatic component. Differing markedly from all reported B. striata polysaccharide, BSP-60 consists of glucose (Glcp) and mannose (Manp) at a molar ratio of 1:1.88, featuring a linear unbranched chain of regularly alternating →4)-Glcp-(1 → and →4)-Manp-(1 → linkages with a polymerization degree of 39, and O-acetyl groups substitute at C2 or C3 of Manp. Combining the results of human washed platelets and aspirin-induced rat gastric bleeding model, BSP-60 markedly activates the G protein-coupled receptors P2Y₁ and P2Y₁₂ to intervenes downstream PLCγ2/PKC and PI3K/Akt signaling cascades, elevating intracellular calcium mobilization, decreasing cAMP levels, and stimulating integrin αIIbβ3 activation, which improves multiple platelet functions and ultimately accelerates hemostasis. Collectively, these findings corroborate that the structurally unique BSP-60 represents the predominant ADP-dependent hemostatic mechanism. Benefiting from its linear unbranched glucomannan architecture, BSP-60 stands as an attractive lead for the development of novel gastric hemostatic drugs.